Hindawi Journal of Chemistry Volume 2018, Article ID 2721752, 10 pages https://doi.org/10.1155/2018/2721752 Research Article Impact Assessment of Phosphogypsum Leachate on Groundwater of Sfax-Agareb (Southeast of Tunisia): Using Geochemical and Isotopic Investigation Samira Melki and Moncef Gueddari Laboratory of Geochemistry and Environmental Geology, Department of Geology, Faculty of Sciences of Tunis, University of Tunis El Manar, 2092 Tunis, Tunisia Correspondence should be addressed to Samira Melki; [email protected] Received 12 November 2017; Accepted 8 January 2018; Published 31 January 2018 Academic Editor: Adina Negrea Copyright © 2018 Samira Melki and Moncef Gueddari. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te production of phosphoric acid by the Tunisian Chemical Group, in Sfax, Tunisia, led to the degradation of the groundwater quality of the Sfax-Agareb aquifer mainly by the phosphogypsum leachates infltration. Spatiotemporal monitoring of the quality of groundwater was carried out by performing bimonthly sampling between October 2013 and October 2014. Samples culled in the current study were subject to physicochemical parameters measurements and analysis of the major elements, orthophosphates, 18 2 fuorine, trace metals, and stable isotopes ( O, H). Te obtained results show that the phosphogypsum leachates infltration has 2− − a major efect on the downstream part of the aquifer, where the highest values of conductivity, SO4 ,Ortho-P,andF ,andthe lowest pH were recorded. In addition, these results indicated that phosphogypsum leachates contained much higher amount of Cr, Cd, Zn, Cu, Fe, and Al compared to the groundwater. Spatiotemporal variation of the conductivity and concentrations of major elements is linked to the phosphogypsum leachates infltration as well as to a wide range of factors such as the natural conditions of 18 2 feeding and the water residence time. Contents of O and H showed that the water of the Sfax-Agareb aquifer undergoes a large scale evaporation process originated from recent rainfall. 1. Introduction In Tunisia, climatic constraints, with a moderate rainfall contribution, which are unequally distributed in the space Groundwater pollution proves to be potentially threatening and irregular in time, as well as a strong evaporation power, as it puts at jeopardy the hygienic integrity of a huge water make water resources limited. Socioeconomic development reserve. Te intensifcation of industrial activities, as well and the spread of industrialization have led to pressuring the as the diversifcation of the storage modes of by-products resources and increasing the demand. Tus, the water supply, 3 production, makes groundwater resources vulnerable and estimated at 472 m /inhabitant in 2010, will decrease to 3 can be considered as the main factors responsible for 315 m /inhabitant in 20 years [6]. In addition, water pollution groundwater pollution. Te groundwater quality is equally relatedtotheincreasedwateruse,urbanandindustrialareas, important as its quantity to the suitability of water for various and agricultural intensifcation is increasingly threatening purposes [1]. Variation of groundwater quality in diferent both the quality and the amount of groundwater resources. regions is a function of physical and chemical parameters Tis phenomenon’s implications are felt in the satisfaction of that are greatly infuenced by geological formations and water demand as well as water cost. anthropogenic activities [2]. Groundwater resources of the Urban, industrial, and tourist centers have been develop- Mediterranean coastal plains in the southern bank of the ing along the eastern coast of Tunisia. Several industries are basin(MiddleEastandNorthAfrica)showaqualitativeand locatedinSfaxarea,especiallythoseoftheTunisianChemical quantitative deterioration developing in time [3–5] resulting Group (TCG) for the enrichment and transformation of in natural constraints and anthropological activities. natural phosphate. Te TCG activity focuses primarily on 2 Journal of Chemistry the chemical fertilizers and phosphoric acid production, amounts of phosphogypsum (PG), issued from the treatment by the fuorapatite transformation. Tis production model of phosphate rock with sulfuric acid [7–14]. Tis chemical generates gaseous emissions, liquid discharges, and huge reaction is illustrated in the equation below: Ca10 (PO4)6 F2 +10H2SO4 +20H2O �→ 1 0 CaSO4 ⋅2H2O +6H3PO4 +2HF (1) Fluorapatite Phosphogypsum Te main environmental contamination associated with PG by standard titration methods [21]. Orthophosphates were dump is fuoride, sulfate, calcium, phosphate, and trace analyzed by absorption colorimeter [21] and fuoride ion elements or radionuclides movement into groundwater [7]. concentrations were measured by specifc electrode [21]. Te scope of this study is to appreciate the PG leachates Te accuracy of the chemical analysis was determined by infltration efect on the Sfax-Agareb aquifer and to identify calculating the ionic balance error, which was generally less the factors and the phenomena, which explain the spatial than 5%. Te trace elements were analyzed using inductivity and the temporal variation of the groundwater quality’s coupled plasma-atomic emission spectrophotometer (ICP- assessment parameters. AES). A summary of the physicochemical and chemical data of all the investigated groundwater during the period 2013- 2 2. Description of the Study Area 2014 is presented in Table 1. Stable isotope analysis of � H and 18 � O was performed by cavity ring down spectrometry using Te study area is situated in the coast of Sfax, where the a Picarro L2120 [22] at the laboratory of Applied Geology and TCG plant, a discharge of domestic waste, and a station of Geo-Environment, Ibn Zohr University, Morocco. wastewater treatment are located (Figure 1). Te study area is under the infuence of the Mediterranean climate, relatively humidandtemperate,withcoldandrainyseasons,between 3.2. Multivariate Statistical Analysis. Te application of mul- December and March, and dry and hot seasons, between tivariate statistical analysis ofers a clearer understanding of JuneandOctober.Teaverageannualprecipitationisaround water quality and enables comparison of the diferent water ∘ 250 mm [15]. Te mean annual temperature is 20 C[16].Te samples [23] and making of correlations between chemi- outcropping geological formations (Figure 2) are composed cal parameters and groundwater samples, respectively. Te of sandy clays rich in gypsum and silty sand [17], of Mio- diferent elements combination (samples and parameters) is Pliocene to lower Quaternary age [18]. Te TCG site takes used in order to characterize the hydrogeochemical variation placeinanareacoveredbyrecentalluvium,madeupbysand of the Sfax-Agareb aquifer, in the site of TCG, in order to and calcareous gypsum crusts. Te Sfax-Agareb aquifer, in predictthefutureofthePGleachatepercolationaswellas this case study, is constituted by two sandy levels, ranging to assess the spatial variation of the groundwater chemical from 2 to 5 m in terms of thickness (Figure 3), separated composition. In this study, only the principal component by clay and sandy layers [19]. Tis aquifer is recharged analysis (PCA) was carried. PCA of the experimental data has by meteoric water. Groundwater fow in the study area is been performed using the Xlstat. Northwest to Southeast. 4. Results and Discussion 3. Materials and Methods 4.1. Characterization of PG Leachate. On global scale, 15% 3.1. Groundwater Sampling and Analysis. Groundwater sam- ofthePGproductionisrecycledwhilelargequantitiesare ples were culled bimonthly from ten piezometers in the stored in the factories vicinity, which are disposed mostly in phreatic aquifer of Sfax-Agareb, between October 2013 and big piles. Tey are located in coastal areas with phosphoric October 2014 (Figure 1). Monitoring piezometers purging acid plants nearby, both as dry or wet staking and without was accomplished by using a submersible pump. Te purge treatment [24]. Since PG waste is generally transported and was achieved when the pH and the electrical conductivity disposed as an aqueous slurry, dissolution/leaching of the (EC) of the ground water have been stabilized. Samples ∘ chemical elements present in the PG can occur. Dissolved taken were acidifed using 0.1 N HNO3 and kept at 4 Cuntil elements may be deposited in nearby soils or transferred the analysis was thoroughly carried out aiming to optimize to groundwater [25]. Tus, it is important to know the the accuracy of the obtained fndings. Te samples were characteristics of leachate obtained from the PG waste dump. analyzed for the following parameters, which include EC, pH, Table 2 lists the chemical composition of a typical sample − 2− − + + 2+ 2+ T, dissolved O 2,Cl ,SO4 ,HCO3 ,Na ,K ,Mg ,Ca , of PG leachate sampling from the GCT site of Sfax. Te − F , and orthophosphates (Ortho-P). EC, pH, and dissolved leachate has a very low pH (1.3) and high concentrations of − oxygen were measured in the feld using calibrated portable fuoride (3500 mg/L), orthophosphate H2PO4 (6730 mg/L), digital meters. Calcium, magnesium, sodium, and potassium and toxic elements (Cd, Cr, and Zn). For all the analyzed were identifed using atomic absorption spectrometer. Car- elements, the levels exceeded the Tunisian standard for liquid bonate, bicarbonate, chloride,